EARTHQUAKE RECORDS

New Zealand Times, Volume LXXI, Issue 4304, 13 March 1901, Page 7

EARTHQUAKE RECORDS

j NOTABLE COINCIDENCES. At the meeting of the Wellington Philosophical Society last night, Mr George Hogbcn delivered an address on “Recent Seismograms of Distant Earthquakes.” Air Hogbcn said he wished to place on record what ho took to bo a notable event in the history of seismology in Australasia. That was the identification of two or three of the tracings of the Milne seismograph in Wellington with those of somewhat similar instrucnts'at European stations. By the recommendation of Sir James Hector, the New Zealand Government ordered two horizontal pendulums for recording one element of the minute or microseismic vibrations that passed round or through the earth. Ouo of theso was placed under his (Air Hogben’s) charge, and it was now installed in a speciallyconstructed room under his private house. Several months were occupied in allowing the masonry column on which tho instrument was placed to settle, and. in testing and adjusting the instrument. It was not. therefore, until October of last year that it was in full working order. Tho instruments at tho central Imperial station for Germany, which was also tho headquarters of the Intel-national Soi.smologioal Association, appeared to have been in working order on the Ist July, 1900. They wore somewhat more sensitive than the Alilno seismograph, and were of the typo known as the Robeur-Ehlort. The essential principle, however, was tho same. Ho had received from Dr Gerlaud, of .Strasburg, and from Dr Schutt, of Hamburg (where Robeur-Ehlort pendulums were also installed) abstracts of tho records of their instruments for the month of October, 1000. Of the fourteen shocks or series of shocks recorded at Sfcrash'urg, Mr Hogben noted clear coincidences with shocks recorded in Wellington in three cases, and more doubtful coincidences in two other cases. One of the earthquakes, from the evidence available so far, seemed to have come from, some place in tho Eastern Pacific, probably from the coast of Peru, though that was puro conjecture. Another was a very considerable earthquake that took place in tho territory of Alaska. It was recorded also at Victoria, British Columbia and at Toronto in Canada by Alilno instruments, and at all the more important European stations. It lasted for over three hours altogether. The Wellington record was consistent with the idea that the vibrations travelled hither along great circles of the earth's crust. The third earthquake was probably from a centre nearer to New Zealand than to Strasburg. It also was probably a Pacific earthquake. There was no difficulty in identifying these by means of the particulars as to time, otc., which he had received from Strasburg. Air Hogben, who exhibited to tho meeting originals and copies of seismograms taken, in V\ ellington, added that it was proposed to issue monthly reports’ here. Permission had been given to have them printed. They would bo distributed to other stations. The weak point of the British Association’s system was that it did not print its records for two years. If records were printed and distributed mouth by month they could be worked out and compared with less labour. To go through them at the end of two years was a very arduous and, in some respects, almost hopeless task. It was hoped that there would be an opportunity iof publishing a synopsis of the AYclliiigton records in the ‘•Transactions of tho New Zealand Institute.” Unfortun-ately-there was no station in Australia as yet. A promise had been given that an instrument would bo set up in Melbourne when funds were available. One was promised for Honolulu without the condition as to funds, and it would probably he erected when the United States authorities had got their scientific affairs in Hawaii into working order. 'The nearest station to Wellington was Batavia. It was desirable that there should be one nearer. Two or three of the records which he exhibited agreed with records taken at Batavia. It might be better if tho British and International Associations co-operated in regard to tho class of instruments used, and in other matters. Probably, however, good, and not harm, would result from, comparing observations made by means of two kinds of instruments. Sir James Hector thanked Mr Hog- 1 hen for giving so clear and early an account of such important observations. A semi-annual movement of-the earth’s crust recorded by the instrument in Wellington was, Sir James thought, very easy of explanation. Air Hogbon’s heuso in Tinakori road was situated right on a major geological fault that traversed New Zealand. The rnocement referred to by Mr Hogben had been noted in connection with transit observations in Wellington since 1867, It was to be hoped that the other instrument. now lying in the Museum, would be put in a place not so liable, to be affected by . geological faults. In conclusion, Sir James said he was extremely glad that a first effort had been made in this matter, and that it was so well advanced under Air Hogben’s care as to promise that in future they would get something like accurate information about earthquakes occurring here and elsewhere.

Mr R. C. Harding expressed the opinion that there should bo no difficulty in improving the method of duplicating records of earthquakes. Air Golem an Phillips; referred to the character of tho numerous earthquakes in the Pacific.

Air Hogben, in reply, said that fortunately tho position of these instruments was not dependent upon such movements as fault movements, as observers could, after a little time, distinguish one kind of movement from another to a very considerable extent. Tho same remark held true in regard to certain earthquakes in the Pacific. A point which observers wished to settle was whether tho first intimation of an earthquake came along tho arc or along tho chord. In tho case of the Alaska record there were overlapping records. An electric system of obtaining numerous seismograms simultaneously had been triad, but it was pronounced a failure, as the lower seismograms were not accurate. •

Tho president (Air G. V. Hudson) thanked Air Hogbcn for his address, and the thanks were emphasised by tho meeting with applause.